This invention relates to a communication line scanning device provided, for a communication controller and more particularly, to a scanning device for scanning a variable number of lines on which data are exchanged at different rates and ensuring the data link control whatever the protocol may be.
Communication controllers are provided to be included in data teleprocessing systems, in order to manage the transmissions performed on the various lines connected thereto. In general, the main control of the teleprocessing network is concentrated in one or several central processing units (CPU) containing a directory of the rules applied for processing data issued from or directed to the terminal units or terminals of the teleprocessing network. Sending and receiving data through communication lines are managed by communication controllers depending on the central processing unit(s). But in addition to the execution of actual transmission controls, the controller is also in charge of executing given directory functions, in particular the functions directly relating to the standard transmission procedures. Due to this fact, the central processing units are exempted from carrying out the corresponding tasks and can be used for executing other works.
The communication controller consists in a sophisticated assembly provided with an intelligence mainly concentrated in one or several central control units (CCU). The central control units are connected, on the one hand, to the terminals through line adapters and, on the other hand, to the central processing units through channel adapters so called because they are connected to the channels of the central processing unit(s).
The line adapters can serve a certain number of lines by means of a cyclic scanning device and a random access memory assembly temporarily containing the data received or to be sent on the various lines as controlled by the scanning device.
In such an environment, each line adapter can be connected to a variable number of lines exchanging information with terminals of various types and therefore, the protocols and the transmission rates of the data on these lines, are different. In order to have a data communication network exhibiting a maximum flexibility, it is necessary to use the same scanning device in the line adapters whatever the number of lines to be scanned and whatever protocols and transmission rates are used on these lines.
In general, for a given communication controller as the IBM 3705 controller, there are provided various types of adapters the design of which depends on the characteristics of the lines connected thereto. It is obvious that this solution is expensive and is affected by a lack of flexibility since when the network configuration is to be modified, it is necessary to change the type of the adapter in function of each configuration.
Therefore an object of this invention is to provide a line scanning device able to scan lines of any type, on which data are exchanged at different rates using different communication protocols.
Another object of this invention is to provide a line scanning device wherein the hardware is minimized.